A 3D printing device based on high-precision partition temperature control and a filament diameter accurate regulation method thereof

Abstract

The application relates to a 3D printing device based on high-precision partition temperature control and a filament diameter accurate regulation method thereof, and relates to the field of additive technology. The application solves the problem of low filament diameter accuracy in the existing high polymer material 3D printing, because the temperature distribution near the printing material is not considered, resulting in poor consistency of the printing filament diameter. The nozzle of the application is mounted at the lower end of the material bin, the push rod is vertically inserted into the material bin and extrudes the high polymer material in the material bin under the pushing force of the push rod; the partition temperature control heating assembly is wrapped on the outer sidewall of the material bin and the nozzle from top to bottom, and partitions the material bin and the nozzle for temperature control; the anti-convection heat exchange shell assembly is buckled on the partition temperature control heating assembly, and the upper part of the anti-convection heat exchange shell assembly is connected with the connecting plate. The rheological test is conducted on the target material to obtain the optimal printing temperature interval, and the high-consistency filament printing is completed. The application is used for additive printing of tissues or organs for transplantation surgery.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, specifically to a 3D printing device based on high-precision zoned temperature control and a method for precisely controlling the filament diameter, for 3D printing of human tissues and organs. Background Technology

[0002] In the biomedical field, tissue engineering technology has become an important tool for regenerative medicine. This technology uses healthy cells and biocompatible materials as raw materials to prepare tissues or organs suitable for transplantation, alleviating the problem of donor shortages. Because tissues and organs typically have complex three-dimensional structures, additive manufacturing technologies, represented by 3D printing, have become the best approach in biomanufacturing. A key feature of this technology is that material is extruded from a cartridge through a nozzle to create continuous filaments with a diameter of several hundred micrometers, which are then deposited onto a platform along a predetermined trajectory, constructing three-dimensional tissue and organ structures through layer-by-layer deposition.

[0003] Because bio-inks are mostly high-molecular polymers with complex rheological properties, they have stringent requirements for printing temperature: if the temperature the material is subjected to during the printing process is too high, the viscosity of that part of the material will decrease, the flowability will increase, and the formability of the printed filaments will deteriorate. In extrusion-based 3D printing, bio-ink material is loaded into a cartridge and heated by the print head. The print head contains a long material flow channel, and its temperature distribution varies spatially due to the location of the heat source, the heat conduction of the mechanical structure, and convective heat transfer with the surrounding air. Since the rheological properties of thermoplastic polymers are very sensitive to temperature changes, the spatial temperature distribution of the print head determines the flowability of the material at different locations.

[0004] When temperature changes are too large, the rheological properties of bio-ink materials can vary significantly at different locations. During the 3D printing process, materials with different flow rates are extruded sequentially from the nozzle to form filaments. The diameter of these filaments varies at different positions along the axial direction, resulting in poor consistency in filament diameter and reduced printing accuracy. As a fundamental component in constructing three-dimensional structures, the errors in these filaments are gradually amplified during 3D printing, causing significant errors in the overall structure and making it difficult to achieve high-precision tissue and organ reconstructions.

[0005] Currently, to mitigate the impact of low filament uniformity on printing results during bio-3D printing, filaments with inconsistent diameters are typically extruded before printing begins. However, this method cannot completely overcome the problem of poor filament uniformity during printing. This phenomenon arises because it ignores the temperature differences between different regions within the print head and fails to implement zoned temperature control for these regional variations. Therefore, to obtain filaments with uniformity, a high-precision zoned temperature control method for the material inside the print head is urgently needed to precisely regulate the filament diameter, improve filament uniformity, and ultimately enhance printing accuracy.

[0006] In summary, existing polymer 3D printing methods fail to consider the temperature distribution near the printing material, resulting in poor consistency in the diameter of the printed filaments and consequently, low filament diameter accuracy. Summary of the Invention

[0007] The purpose of this invention is to solve the problem that in existing polymer 3D printing, the temperature distribution near the printing material is not considered, resulting in poor consistency of the printed filament diameter and thus low filament diameter accuracy. Therefore, this invention provides a 3D printing device based on high-precision zoned temperature control and a method for precise control of the filament diameter.

[0008] The technical solution of this invention is:

[0009] A 3D printing device based on high-precision zoned temperature control includes a connecting plate, a material hopper, an anti-convection heat exchange shell assembly, a zoned temperature control heating assembly, a nozzle, and a push rod. The nozzle is installed at the lower end of the material hopper, and the push rod is vertically inserted into the material hopper. Under the pushing force of the push rod, the polymer material in the material hopper is extruded to form filaments with a diameter of 0.15-0.25 mm. The zoned temperature control heating assembly wraps around the outer walls of the material hopper and the nozzle from top to bottom and controls the temperature of the material hopper and the nozzle in zones. The anti-convection heat exchange shell assembly is fastened to the zoned temperature control heating assembly, and the upper part of the anti-convection heat exchange shell assembly is connected to the connecting plate.

[0010] Preferably, the diameter of the hopper opening gradually decreases from top to bottom, and an annular groove is provided on the bottom surface of the hopper, with the nozzle being fitted onto the annular groove.

[0011] Furthermore, the zoned temperature control heating assembly includes an upper heating device in the silo, a lower heating device in the silo, and a heating device at the nozzle. The upper heating device in the silo and the lower heating device in the silo are mounted on the silo from top to bottom, and the heating device at the nozzle is mounted at the connection between the nozzle and the silo.

[0012] Furthermore, the anti-convective heat exchange shell assembly includes an outer shell assembly and an inner shell assembly. The inner shell assembly is wrapped around the zoned temperature control heating assembly, and the outer shell assembly is fastened onto the inner shell assembly.

[0013] Furthermore, the internal housing assembly includes an upper heating housing in the hopper, a lower heating housing in the hopper, and a nozzle heating housing, which respectively wrap around the upper heating device in the hopper, the lower heating device in the hopper, and the nozzle heating device.

[0014] Furthermore, the external housing assembly includes a first anti-convection heat exchange housing, a second anti-convection heat exchange housing, and a third anti-convection heat exchange housing. The third anti-convection heat exchange housing is installed on the nozzle and on the nozzle heating housing. The first anti-convection heat exchange housing is installed on the upper heating housing and the lower heating housing of the hopper.

[0015] Preferably, a boss is machined on the upper part of the outer circumferential sidewall of the silo, and an inverted truncated cone with a gradually decreasing diameter is machined on the lower part of the outer circumferential sidewall of the silo.

[0016] This invention also provides a method for precisely controlling the filament diameter using a 3D printing device based on high-precision zoned temperature control, which includes the following steps:

[0017] Step 1: Obtain the modulus-temperature profile;

[0018] Using a rotational rheometer with temperature control, the curve of the complex modulus as a function of temperature was obtained by vibration temperature scanning analysis of the target material.

[0019] Step 2: Determine the optimal printing temperature range;

[0020] Analyze the curve of the modulus as a function of temperature to find and determine the most suitable temperature for 3D printing;

[0021] Step 3: Obtain the printing filaments under different printing parameters;

[0022] Within the optimal temperature range for printing, select two temperature control variables:

[0023] First, set the upper and lower parts of the silo to the same temperature, as the first temperature variable;

[0024] Secondly, set the nozzle temperature as the second variable;

[0025] Step 4: Analyze the consistency of the printed filament diameter;

[0026] Step 41: Print out filaments of the same length, remove the poorly formed parts of the entire filament, and record the length of the well-formed parts;

[0027] Step 42: The ratio of the length of the formed portion to the length of the entire filament is used as an indicator to measure the consistency of the filament diameter. The higher the ratio, the more poorly formed areas there are in the printed filament, the worse the filament consistency, and the lower the printing accuracy; conversely, the same applies.

[0028] Step 5: Organize the experimental data, and use the two temperature variables and the consistency index of different experimental groups as the coordinate values ​​of x, y and z respectively to obtain a set of three-dimensional bar charts; import the experimental data in the three-dimensional bar charts into the analysis software, and fit the change surface of the consistency index under different temperature variables to obtain a predictive model for controlling the filament diameter by adjusting the two printing parameters.

[0029] Step Six: Optimize printing parameters using a predictive model:

[0030] First, determine the consistency index of the target filaments for printing. Then, based on this index, select an appropriate temperature on the surface of the prediction model as the high-precision printing parameter for the target material filaments.

[0031] Step 7: 3D print the target material using this parameter and determine whether the printing accuracy meets the requirements. This completes the verification of the filament diameter precision control method based on high-precision zoned temperature control.

[0032] Furthermore, the analysis process for the curve of the complex modulus changing with temperature in step two is as follows:

[0033] Due to the special nature of polymer materials, they exhibit both Newtonian viscosity and Hooke's elasticity in their physical properties, i.e., the viscoelasticity of polymer materials; the complex modulus is a rheological property used to describe the viscoelasticity of polymer materials, and is divided into storage modulus (G') and dissipation modulus (G”).

[0034] Among them, the storage modulus is used to measure the Hooke's elasticity of a material, and the dissipation modulus is used to measure the Newtonian viscosity of a material.

[0035] When G' is greater than G", the Hooke's elasticity of the material dominates, and the material exhibits elasticity similar to that of a solid. At this time, the material has poor fluidity, causing the printing filament to undergo plastic deformation, resulting in the filament expanding and breaking.

[0036] When G' is less than G", the Newtonian viscosity of the material dominates, and the material exhibits a liquid-like fluidity. At this time, the ability to form filaments printed is relatively weak.

[0037] Furthermore, in step two, the optimal temperature range for 3D printing is determined as follows:

[0038] The temperature range within ±3.5℃ where the G' and G” curves intersect is the most suitable range for 3D printing of polymer materials.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] 1. This invention obtains the optimal printing temperature range by conducting rheological tests on the target material, and achieves 3D printing of the target material under different parameters by building a 3D printing device that can control the local temperature at different positions of the printing nozzle, while recording the consistency of the printed filaments. Based on the experimental data, a printing accuracy prediction model is constructed and the printing parameters are optimized to complete the printing of filaments with high filament consistency and high diameter accuracy.

[0041] 2. This invention proposes a method to improve the consistency of 3D printed filaments by setting partitioned temperature control to achieve precise regulation of the filament diameter. The partitioned temperature control is achieved through individual and precise control of the upper heating device 3 in the material hopper, the lower heating device 4 in the material hopper, and the heating device 5 at the nozzle. This design method enables high-precision printing of polymer filaments, with a simple and clear design process and high efficiency in obtaining optimal parameters. It is of great significance for the high-precision in vitro construction of complex tissues and organs.

[0042] 3. For example Figures 1 to 5 As shown, the optimal printing temperature range was determined through rheological testing; the relationship between filament consistency and process parameters was investigated by constructing a 3D printing device capable of controlling the local temperature at different locations. Poly(L-lactide-caprolactone) (PLCL), a commonly used polymer in biomanufacturing, was used as the printing material to verify the feasibility of the designed method. Figure 3 The results of the printing experiment are shown below. The results were analyzed using a computer, and a fitting was obtained as shown below. Figure 4 The prediction model is shown. Based on the prediction model, parameters were optimized and filament printing experiments were conducted, ultimately resulting in... Figure 5 As shown, this method improves the consistency of the filaments. Without it, the diameter consistency index of the printed PLCL filaments is only 0.77, while with this method, the diameter consistency index reaches over 0.95, effectively improving the diameter accuracy of 3D printed filaments. Attached Figure Description

[0043] Figure 1 This is a flowchart of the method for precisely controlling the wire diameter of the present invention;

[0044] Figure 2 This is a schematic diagram of the overall structure of a 3D printing device based on high-precision zoned temperature control according to the present invention.

[0045] Figure 3 This is a curve showing the change in modulus of PLCL material (i.e., poly-L-lactide-caprolactone) with temperature.

[0046] Figure 4 It is an indicator of the consistency of filament diameter in 3D printed PLCLs under different local temperature controls;

[0047] Figure 5 It is a PLCL filament accuracy prediction model under different local temperature control conditions;

[0048] Figure 6 It is a high-precision PLCL filament with different printing filament consistency.

[0049] The components are: 1. Connecting plate, 2. First anti-convection heat exchange shell, 3. Upper heating device in the hopper, 4. Lower heating device in the hopper, 5. Heating device at the nozzle, 6. Second anti-convection heat exchange shell, 7. Nozzle, 8. Third anti-convection heat exchange shell, 9. Nozzle heating shell, 10. Lower heating shell in the hopper, 11. Hopper, 11-1. Boss, 11-2. Inverted cone, 12. Upper heating shell in the hopper, 13. Push rod. Detailed Implementation

[0050] Specific implementation method one: Combining Figure 2 This embodiment includes a connecting plate 1, a hopper 11, an anti-convection heat exchange shell assembly, a zoned temperature control heating assembly, a nozzle 7, and a push rod 13. The nozzle 7 is installed at the lower end of the hopper 11. The push rod 13 is vertically inserted into the hopper 11 and, under the pushing force of the push rod 13, extrudes the polymer material in the hopper 11 to form fine filaments with a diameter of 0.15-0.25 mm. The zoned temperature control heating assembly wraps around the outer walls of the hopper 11 and the nozzle 7 from top to bottom and controls the temperature of the hopper 11 and the nozzle 7 in zones. The anti-convection heat exchange shell assembly is fastened to the zoned temperature control heating assembly, and the upper part of the anti-convection heat exchange shell assembly is connected to the connecting plate 1.

[0051] In this embodiment, the push rod 13 is pushed downwards at a uniform speed by an external lifting device, ensuring that the polymer material is extruded at a uniform speed at the nozzle 7. Moreover, the vertical reciprocating motion of the push rod 13 realizes the pushing and extrusion of the target material, completing the 3D printing process. The connecting plate 1 is located on the outside of the anti-convection heat exchange shell assembly and is connected to the anti-convection heat exchange shell assembly by welding or bolting, which is a simple and reliable connection method.

[0052] In this embodiment, a zoned temperature control heating component is used to achieve independent control of the local temperature in the nozzle 7 and the material hopper 11. To ensure the accuracy of the temperature control position selection, the entire zoned temperature control heating component is mainly located in the lower middle part of the material hopper 11, ensuring the stability requirements of the material hopper 11 and the nozzle 7. The overall temperature distribution inside the printing head is adjusted at the nozzle 7, thereby controlling the target material to receive uniform heating temperature.

[0053] Specific Implementation Method Two: Combining Figure 2In this embodiment, the diameter of the hopper 11 gradually decreases from top to bottom, and an annular groove is provided on the bottom surface of the hopper 11, on which the nozzle 7 is fitted. This design, with its gradually decreasing hopper diameter, facilitates rapid material extrusion, and the annular groove provides convenience for the installation and removal of the nozzle 7. Other components and connections are the same as in specific embodiment one.

[0054] Specific implementation method three: Combining Figure 2 This embodiment describes a zoned temperature control heating assembly that includes an upper heating device 3 in the silo, a lower heating device 4 in the silo, and a nozzle heating device 5. The upper heating device 3 and the lower heating device 4 are mounted on the silo 11 from top to bottom, and the nozzle heating device 5 is mounted at the connection between the nozzle 7 and the silo 11.

[0055] This configuration facilitates independent and precise temperature control of the material hopper 11 and nozzle 7, providing the necessary conditions for the quality of filament extrusion and avoiding the problem of inconsistent material physical states caused by different temperatures in different parts, which in turn affects the inconsistent quality of the printed filaments. Other components and connections are the same as in specific embodiments one or two.

[0056] In this embodiment, the upper heating device 3, the lower heating device 4, and the nozzle heating device 5 in the hopper include, but are not limited to, heating rods, heating wires, etc., and are all equipped with temperature measuring devices, which can achieve precise temperature control at local locations.

[0057] Specific implementation method four: Combination Figure 2 This embodiment describes an anti-convective heat exchange shell assembly comprising an outer shell assembly and an inner shell assembly. The inner shell assembly is wrapped around the zoned temperature control heating assembly, and the outer shell assembly is fastened onto the inner shell assembly.

[0058] This configuration employs double-layer temperature protection to prevent heat loss and enables rapid heating of the outer wall of the hopper 11, as well as localized surface heating of the area to be heated. Other components and connections are the same as in any of the specific embodiments one to three.

[0059] Specific Implementation Method Five: Combining Figure 2 This embodiment describes an internal housing assembly comprising an upper heating housing 12 in the hopper, a lower heating housing 10 in the hopper, and a nozzle heating housing 9. The upper heating housing 12 in the hopper, the lower heating housing 10 in the hopper, and the nozzle heating housing 9 are respectively wrapped around the upper heating device 3 in the hopper, the lower heating device 4 in the hopper, and the heating device 5 at the nozzle.

[0060] This design facilitates wrapping around the heating device, improving heating efficiency. Other components and connections are the same as in any of the first to fourth embodiments.

[0061] Specific Implementation Method Six: Combination Figure 2 This embodiment describes an external housing assembly comprising a first anti-convection heat exchange shell 2, a second anti-convection heat exchange shell 6, and a third anti-convection heat exchange shell 8. The third anti-convection heat exchange shell 6 is mounted on the nozzle 7, and the third anti-convection heat exchange shell 8 is mounted on the nozzle heating shell 9. The first anti-convection heat exchange shell 2 is mounted on the upper heating shell 12 and the lower heating shell 10 of the hopper.

[0062] In this configuration, the 3D printing nozzle of the present invention heats the internal material through a heating device equipped with heating rods or the like. Since the background of this invention is bio-3D printing, a high degree of cleanliness needs to be maintained during the printing process. Therefore, airflow is often required during high-temperature 3D printing. Once the printing device is exposed to flowing air, forced convection heat transfer occurs, causing the heat generated by the heating device to be lost to the flowing air, resulting in unstable heating and poor heating effect. Therefore, an anti-convection heat transfer shell needs to be installed on the outside of the heating device to avoid the influence of external environmental disturbances on heating. Other components and connections are the same as in any of the specific embodiments one to five.

[0063] Specific implementation method seven: Combining Figure 2 In this embodiment, a boss 11-1 is machined on the upper part of the outer circumferential sidewall of the hopper 11, and a gradually decreasing diameter inverted frustum 11-2 is machined on the lower part of the outer circumferential sidewall of the hopper 11. This arrangement allows the boss 11-1 to effectively save space, providing space and limiting the installation of the anti-convective heat exchange shell assembly and the zoned temperature control heating assembly. The design of the inverted frustum 11-2 makes the heating area of ​​the hopper 11 progressively smaller, facilitating a faster heating rate. Other components and connections are the same as in any of the specific embodiments one through six.

[0064] Specific implementation method eight: Combination Figure 2 This embodiment describes a method for precisely controlling the wire diameter, which includes the following steps:

[0065] Step 1: Obtain the modulus-temperature profile;

[0066] Using a rotational rheometer with temperature control, the curve of the complex modulus as a function of temperature was obtained by vibration temperature scanning analysis of the target material.

[0067] Step 2: Determine the optimal printing temperature range;

[0068] Analyze the curve of the modulus as a function of temperature to find and determine the most suitable temperature for 3D printing;

[0069] Step 3: Obtain the printing filaments under different printing parameters;

[0070] Within the optimal temperature range for printing, select two temperature control variables:

[0071] First, the upper and lower parts of the hopper 11 are set to the same temperature, which is the first temperature variable;

[0072] Secondly, the temperature of nozzle 7 is set as the second variable;

[0073] Step 4: Analyze the consistency of the printed filament diameter;

[0074] Step 41: Print out filaments of the same length, remove the poorly formed parts of the entire filament, and record the length of the well-formed parts;

[0075] Step 42: The ratio of the length of the formed portion to the length of the entire filament is used as an indicator to measure the consistency of the filament diameter. The higher the ratio, the more poorly formed areas there are in the printed filament, the worse the filament consistency, and the lower the printing accuracy; conversely, the same applies.

[0076] Step 5: Organize the experimental data, and use the two temperature variables and the consistency index of different experimental groups as the coordinate values ​​of x, y and z respectively to obtain a set of three-dimensional bar charts; import the experimental data in the three-dimensional bar charts into the analysis software, and fit the change surface of the consistency index under different temperature variables to obtain a predictive model for controlling the filament diameter by adjusting the two printing parameters.

[0077] Step Six: Optimize printing parameters using a predictive model:

[0078] First, determine the consistency index of the target filaments for printing. Then, based on this index, select an appropriate temperature on the surface of the prediction model as the high-precision printing parameter for the target material filaments.

[0079] Step 7: 3D print the target material using this parameter and determine whether the printing accuracy meets the requirements. This completes the verification of the filament diameter precision control method based on high-precision zoned temperature control.

[0080] Specific Implementation Method Nine: Combining Figure 2 The following describes the process of analyzing the curve of the composite modulus changing with temperature in step two of this embodiment:

[0081] Due to the special nature of polymer materials, they exhibit both Newtonian viscosity and Hooke's elasticity in their physical properties, i.e., the viscoelasticity of polymer materials; the complex modulus is a rheological property used to describe the viscoelasticity of polymer materials, and is divided into storage modulus (G') and dissipation modulus (G”).

[0082] Among them, the storage modulus is used to measure the Hooke's elasticity of a material, and the dissipation modulus is used to measure the Newtonian viscosity of a material.

[0083] When G' is greater than G", the Hooke's elasticity of the material dominates, and the material exhibits elasticity similar to that of a solid. At this time, the material has poor fluidity, causing the printing filament to undergo plastic deformation, resulting in the filament expanding and breaking.

[0084] When G' is less than G", the Newtonian viscosity of the material dominates, and the material exhibits a liquid-like fluidity. At this time, the ability to form filaments printed is relatively weak.

[0085] This configuration ensures that the 3D-printed material neither flows everywhere nor becomes rigid. It maintains consistent fluidity and is extruded into the 3D printing substrate in filament form. Other components and connections are the same as in any of the specific embodiments one through eight.

[0086] Specific Implementation Method Ten: Combining Figure 2 This embodiment describes the process of determining the optimal temperature range for 3D printing in step two.

[0087] The optimal temperature range for 3D printing polymer materials is ±3.5°C when the G' and G” curves intersect. This setting ensures that the 3D printed material neither flows excessively nor becomes rigid. It maintains consistent fluidity and is extruded into the 3D printing substrate in filament form. Other components and connections are the same as in any of the specific embodiments one through nine.

[0088] Combination Figures 1 to 6 Explanation of the working process of this invention:

[0089] Step 1: Using a rotational rheometer with temperature control, the target material is subjected to vibration temperature scanning analysis to obtain the curve of the complex modulus changing with temperature.

[0090] Step Two: Analyze the curve of complex modulus versus temperature to find the optimal temperature for 3D printing. Due to the special nature of polymer materials, they often exhibit both Newtonian viscosity and Hooke's elasticity in their physical properties, i.e., viscoelasticity. Complex modulus is a rheological property used to describe the viscoelasticity of polymer materials, and it is divided into storage modulus (G') and dissipation modulus (G"). Storage modulus measures the Hooke's elasticity, while dissipation modulus measures the Newtonian viscosity. When G' is greater than G"', the Hooke's elasticity dominates, and the material exhibits elasticity similar to a solid. At this point, the material's flowability is poor, causing plastic deformation of the printed filament, leading to filament expansion and breakage. When G' is less than G"', Newtonian viscosity dominates, and the material exhibits fluidity similar to a liquid. At this point, the printed filament has weaker forming ability. Therefore, by analyzing the curve of complex modulus versus temperature, it is concluded that the temperature range near the intersection of the G' and G" curves is the most suitable range for 3D printing of polymer materials.

[0091] To achieve zoned temperature control based on temperature differences in different areas, a novel 3D printing device was developed that can independently control the temperature of different positions on the printing nozzle. The mechanical structure of this device is as follows: Figure 2 As shown, the connection relationship is as follows: the connecting plate 1 serves as the connection between the 3D printing nozzle and the 3D printer, allowing the proposed 3D printing equipment to be connected to the printing device. The hopper 11 is connected to the lower end of the connecting plate 1. Its exterior is sequentially wrapped from top to bottom with an upper heating shell 12 made of high thermal conductivity metal material, a lower heating shell 10, and a nozzle heating shell 9. Inside these shells, the upper heating device 3, the lower heating device 4, and the nozzle heating device 5 are installed sequentially. The nozzle 7 is connected to the bottom end of the hopper 11. A second anti-convection heat exchange shell 6 is fixed to the outside of the nozzle 7. The push rod 13 is inserted into the hopper 11 and can move axially along the internal channel of the hopper 11. The first anti-convection heat exchange shell 2 is installed at the bottom end of the connecting plate 1, located on the outermost side of the overall structure. The third anti-convection heat exchange shell 8 is installed at the bottom end of the overall structure. The connection methods mentioned above include, but are not limited to, threaded connection, welding, pin connection, etc.; the heating methods of the upper heating device 3 in the hopper, the lower heating device 4 in the hopper, and the heating device 5 at the nozzle include, but are not limited to, heating rods, heating wires, etc., and all are equipped with temperature measuring devices, which can realize precise temperature control of local positions.

[0092] The working process is as follows: The target material is loaded into the hopper 11, and the overall temperature distribution inside the printing nozzle is adjusted by regulating the upper heating device 3, the lower heating device 4, and the nozzle heating device 5, thereby controlling the target material to receive uniform heating. The vertical reciprocating motion of the push rod 13 realizes the pushing and extrusion of the target material, completing the 3D printing process.

[0093] Step 3: Using this printing equipment, adjust the local temperature at different locations inside the print head to control the temperature of the printing material in different areas of the hopper, and then proceed with printing. Within the optimal printing temperature range, select two temperature control variables: first, set the upper and bottom of the hopper to the same temperature; second, set the temperature near the nozzle as the second variable. Obtain the printed filament under different printing parameters.

[0094] Step 4: Analyze the diameter consistency of the printed filaments. First, print filaments of the same length. Remove the poorly formed portions of the entire filament and record the length of the well-formed portions. The ratio of the length of the well-formed portions to the total length of the filament will be used as an indicator of filament diameter consistency. The higher this ratio, the more poorly formed areas there are in the printed filament, the worse the filament consistency, and the lower the printing accuracy.

[0095] Step 5: Organize the experimental data. Use the two temperature variables and the consistency index of different experimental groups as x, y, and z coordinate values ​​respectively to obtain a set of three-dimensional bar charts. Import the experimental data in this chart into the analysis software and fit the curve of the consistency index under different temperature variables to obtain a predictive model for controlling the filament diameter by adjusting the two printing parameters.

[0096] Step 6: The printing parameters can be optimized through the prediction model: First, the consistency index of the target printing filament is determined, and then a suitable temperature is selected on the surface of the prediction model based on the index as the high filament precision printing parameter for the target material.

[0097] Step 7: 3D print the target material using this parameter and determine whether the printing accuracy meets the requirements. This completes the verification of the filament diameter precision control method based on high-precision zoned temperature control.

[0098] Example:

[0099] Printing material: a biodegradable polymer

[0100] Poly(L-lactide-caprolactone) (PLCL)

[0101] The purchased PLCL particles were placed in a rotational rheometer, and the complex modulus-temperature curve of the PLCL was obtained using the oscillating temperature scan analysis mode. Figure 3 )

[0102] Based on the obtained curves, 130℃-137℃ was selected as the optimal printing temperature. Therefore, a 3D printing experiment was conducted using a 9-nozzle temperature-hopper temperature group to calculate the consistency of the printed filaments, and the printing results were recorded. Figure 4 ).

[0103] The obtained data is input into the analysis software, and the surface is obtained through fitting. Figure 5 Two sets of printing parameters were selected for the curved surface, one with the best consistency (material hopper and nozzles at 137°C) and the other with the worst consistency (material hopper and nozzles at 130°C). Printing experiments were conducted. The final experimental results ( Figure 6 This verified its feasibility.

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for precisely controlling the filament diameter of a 3D printing device based on high-precision zoned temperature control, wherein the 3D printing device based on high-precision zoned temperature control includes a connecting plate (1), a hopper (11), an anti-convection heat exchange shell assembly, a zoned temperature control heating assembly, a nozzle (7), and a push rod (13). The nozzle (7) is installed at the lower end of the hopper (11), and the push rod (13) is vertically inserted into the hopper (11). Under the pushing force of the push rod (13), the polymer material in the hopper (11) is extruded to form a fine filament with a diameter of 0.15-0.25mm. The zone temperature control heating component is wrapped around the outer wall of the hopper (11) and the nozzle (7) from top to bottom, and the zone temperature control is applied to the hopper (11) and the nozzle (7). The anti-convection heat exchange shell component is fastened to the zone temperature control heating component, and the upper part of the anti-convection heat exchange shell component is connected to the connecting plate (1). The zoned temperature control heating assembly includes an upper heating device (3) in the silo, a lower heating device (4) in the silo, and a nozzle heating device (5). The upper heating device (3) and the lower heating device (4) in the silo are mounted on the silo (11) from top to bottom, and the nozzle heating device (5) is mounted at the connection between the nozzle (7) and the silo (11). Its features are: The method for precisely controlling the wire diameter includes the following steps: Step 1: Obtain the modulus-temperature profile; Using a rotational rheometer with temperature control, the curve of the complex modulus as a function of temperature was obtained by vibration temperature scanning analysis of the target material. Step 2: Determine the optimal printing temperature range; Analyze the curve of the modulus as a function of temperature to find and determine the most suitable temperature for 3D printing; Step 3: Obtain the printing filaments under different printing parameters; Within the optimal temperature range for printing, select two temperature control variables: Firstly, the upper part and the lower part of the silo (11) are set to the same temperature as the first temperature variable; Secondly, the temperature of the nozzle (7) is set as the second variable; Step 4: Analyze the consistency of the printed filament diameter; Step 41: Print out filaments of the same length, remove the poorly formed parts of the entire filament, and record the length of the well-formed parts; Step 42: The ratio of the length of the formed portion to the length of the entire filament is used as an indicator to measure the consistency of the filament diameter. The higher the ratio, the more poorly formed areas there are in the printed filament, the worse the filament consistency, and the lower the printing accuracy; conversely, the same applies. Step 5: Organize the experimental data, and use the two temperature variables and the consistency index of different experimental groups as the coordinate values ​​of x, y and z respectively to obtain a set of three-dimensional bar charts; import the experimental data in the three-dimensional bar charts into the analysis software, and fit the change surface of the consistency index under different temperature variables to obtain a predictive model for controlling the filament diameter by adjusting the two printing parameters. Step Six: Optimize printing parameters using a predictive model: First, determine the consistency index of the target filaments for printing. Then, based on this index, select an appropriate temperature on the surface of the prediction model as the high-precision printing parameter for the target material filaments. Step 7: 3D print the target material using this parameter and determine whether the printing accuracy meets the requirements. This completes the verification of the filament diameter precision control method based on high-precision zoned temperature control.

2. The method for precisely controlling the wire diameter according to claim 1, characterized in that: The analysis process for the curve of the change of the complex modulus with temperature in step two is as follows: Due to the special nature of polymer materials, they exhibit both Newtonian viscosity and Hooke's elasticity in their physical properties, i.e., viscoelasticity of polymer materials; complex modulus is used to describe the rheological properties of viscoelasticity of polymer materials, and is divided into storage modulus (G') and dissipation modulus (G”). Among them, the storage modulus is used to measure the Hooke's elasticity of a material, and the dissipation modulus is used to measure the Newtonian viscosity of a material. When G' is greater than G", the Hooke's elasticity of the material dominates, and the material exhibits elasticity similar to that of a solid. At this time, the material has poor fluidity, causing the printing filament to undergo plastic deformation, resulting in the filament expanding and breaking. When G' is less than G", the Newtonian viscosity of the material dominates, and the material exhibits a liquid-like fluidity. At this time, the ability to form filaments printed is relatively weak.

3. The method for precisely controlling the wire diameter according to claim 2, characterized in that: In step two, the optimal temperature range for 3D printing is determined as follows: The temperature range within ±3.5℃ where the G' and G” curves intersect is the most suitable range for 3D printing of polymer materials.

4. The method for precisely controlling the wire diameter according to claim 1, characterized in that: The diameter of the hopper (11) gradually decreases from top to bottom, and an annular groove is provided on the bottom surface of the hopper (11), and the nozzle (7) is fitted on the annular groove.

5. The method for precisely controlling the wire diameter according to claim 4, characterized in that: The anti-convective heat exchange shell assembly includes an outer shell assembly and an inner shell assembly. The inner shell assembly is wrapped around the zoned temperature control heating assembly, and the outer shell assembly is fastened onto the inner shell assembly.

6. The method for precisely controlling the wire diameter according to claim 5, characterized in that: The internal housing assembly includes an upper heating housing (12) in the hopper, a lower heating housing (10) in the hopper, and a nozzle heating housing (9). The upper heating housing (12), the lower heating housing (10), and the nozzle heating housing (9) are respectively wrapped around the upper heating device (3), the lower heating device (4), and the nozzle heating device (5).

7. The method for precisely controlling the wire diameter according to claim 6, characterized in that: The external housing assembly includes a first anti-convection heat exchange shell (2), a second anti-convection heat exchange shell (6), and a third anti-convection heat exchange shell (8). The second anti-convection heat exchange shell (6) is installed on the nozzle (7), the third anti-convection heat exchange shell (8) is installed on the nozzle heating shell (9), and the first anti-convection heat exchange shell (2) is installed on the upper heating shell (12) and the lower heating shell (10) of the silo.

8. The method for precisely controlling the wire diameter according to claim 7, characterized in that: The upper part of the outer circumferential side wall of the hopper (11) is machined with a boss (11-1), and the lower part of the outer circumferential side wall of the hopper (11) is machined with an inverted cone (11-2) with a gradually decreasing diameter.

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